As urbanization increases, urban runoff becomes an increasingly more important component of urban non-point pollution. In this study, the Storm Water Management Model was used to simulate the quantity and quality of runoff in a highly urbanized catchment. Data from three rainfall events were collected and used for model calibration and validation. Model performance was assessed using the Nash-Sutcliffe coefficient, relative error, and coefficient of determination. The modified Morris screening method was used for local sensitivity analysis. Sensitivity analysis results showed that the destore imperv and condit roughness parameters had the most influence on the hydrology and hydraulic module. Road exponent was the most sensitive parameter in determining TSS quantity and peak concentration. The calibration and verification results indicated that the model structure and parameters fitted the runoff-producing pattern. The total simulation accuracies of TSS, TN, TP, and COD loads, as assessed by the R² value, were 0.82, 0.87, 0.72, and 0.94, respectively.